Solar heating apparatus

ABSTRACT

A solar heating apparatus is disclosed that, in one embodiment, comprises a heating coil with improved heating efficiency comprising a first lateral tube comprising rounded ends and an elliptical cross section for a portion extending between the ends that is connected by a rounded end cap to a second lateral tube also comprising rounded ends and an elliptical cross section for a portion extending between the ends.

BACKGROUND OF THE INVENTION

The subject matter herein relates generally to solar heating systems.More particularly, the subject matter disclosed herein relates to animproved heating coil for use in flat panel solar collectors.

The ever increasing costs associated with conventional heating systemsas well as global concerns regarding greenhouse gas emissions havefueled intense interest in cheap, clean solar energy solutions.Conventional solar powered heating systems typically employ flat panelsolar collectors having a heating coil through which water iscirculated. Cool water is pumped into the solar panel where energy fromthe sunlight incident on the solar panel warms the heating coil, which,in turn, transfers heat to the water flowing within it. The heated waterthen exits the solar panel and is then used, stored in an insulatedstorage container for later use, or run through a heat exchanger wherethe captured heat is again transferred to another medium.

Although solar heating technologies have existed for many years,drawbacks to conventional solar heating systems have hampered wide scaleadoption of the technology. For example, due to their inefficiencies,conventional solar heating systems require significant surface areacoverage in order to generate sufficient volumes of heated fluid. Thisnecessitates using either large solar panels or groups of smaller solarpanels for which initial installation and maintenance costs can be high.Various attempts have been made to improve the efficiency ofconventional solar panels, such as the use of heating coils withmodified geometries that increase the heat transfer surface area of thecoil to improve overall heat absorption by the fluid, but such systemsstill exhibit drawbacks. For example, some hot water solar panels employheating coils made of tubes having an elliptical cross section, asopposed to a rounded cross section, that are aligned in a side-by-sideconfiguration and interconnected with a header on each end. Water isforced into one header, which directs the water through each of thetubes and into the other header where it then exits the panel. As such,although the modified structure of the heating coil works to improveheat transfer, the overall configuration, which only allows water toflow across the panel once in a single direction, leaves the overallefficiency of the panel low.

Additionally, the use of complex, custom designed components in manyconventional solutions requires complicated interconnections betweenfluid transmitting parts, increasing initial manufacturing andinstallation costs, as well as long term maintenance costs. Anotherdrawback to conventional systems is that consumers are often deterred bythe aesthetic impact the large, and often numerous, solar panels have ontheir property.

It would be advantageous to provide a flat panel solar collector thatprovides better heating efficiency per square foot of panel coverage,and that has low installation and maintenance costs

BRIEF DESCRIPTION OF THE INVENTION

An apparatus for heating a fluid using solar energy is disclosed, in oneembodiment comprising an absorption plate exposed to the solar energy,and a heating coil, the heating coil comprising a first lateral tubecomprising a cylindrical first end portion, a cylindrical second endportion, a flattened top portion, and a flattened bottom portion, theflattened bottom portion being in contact with the absorption plate, asecond lateral tube comprising a cylindrical first end portion, acylindrical second end portion, a flattened top portion, and a flattenedbottom portion, the flattened bottom portion being in contact with theabsorption plate, and a cylindrical end cap connecting the second endportion of the first lateral tube to the second end portion of thesecond lateral tube such that fluid flowing through the first lateraltube in a first direction is redirected by the end cap into the secondlateral tube in a second direction. In one embodiment the heating coilcan be comprised of a single piece of continuous conduit, while in otherembodiments the heating coil can be comprised of multiple pieces ofconduit that have been joined together.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features of the invention can beunderstood, a detailed description of the invention may be had byreference to certain embodiments, some of which are illustrated in theaccompanying drawings. It is to be noted, however, that the drawingsillustrate only certain embodiments of this invention and are thereforenot to be considered limiting of its scope, for the scope of theinvention encompasses other equally effective embodiments. The drawingsare not necessarily to scale, emphasis generally being placed uponillustrating the features of certain embodiments of invention. Thus, forfurther understanding of the invention, reference can be made to thefollowing detailed description, read in connection with the drawings inwhich:

FIG. 1 is a block diagram of an exemplary solar heating system in oneembodiment of the invention.

FIG. 2 is a perspective view of an exemplary flat panel solar collectorin one embodiment of the invention.

FIG. 3 is a block diagram of an exemplary solar heating system with heatexchanger in one embodiment of the invention.

FIG. 4 is a cross section of an exemplary heating coil in one embodimentof the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an exemplary solar heating system 10 in one embodiment ofthe invention. Solar heating system 10 can comprise a cold fluid inlet220 that can allow cold (unheated) fluid, for example water, to enter astorage tank 200. Storage tank 200 can be a thermally insulated tankthat minimizes heat loss from its contents. In some embodiments, storagetank 200 can provide fluid heating capabilities of its own through, forexample, a natural gas burner or electric heating element (not shown).System control 280 can be a timer, a thermostat, a photodetector fordetecting sunlight 250 incident on solar collector 100, or a combinationof one or more of these elements, and can be in electrical communicationwith both storage tank 200 and a pump 210. Pump 210 can be anelectrically powered pump that forces fluid out of storage tank 200through a cold fluid outlet 260, through a solar panel inlet 265,through a coil inlet 165, through a solar collector 100, through a coiloutlet 175, through a hot fluid inlet 270, and back into storage tank200. System control 280 can monitor various physical parameters andactive and deactivate pump 210 in response to those parameters. In oneembodiment, pump 210 can be located along storage outlet 260, and can beactivated by system control 280 when it senses either that thetemperature within storage tank 200 is below an established threshold,when sunlight 250 is detected as being incident on solar collector 100,when a given time period has expired, or any combination of thesefactors. Heated water exits storage tank 200 through hot fluid outlet230. Cold fluid inlet 220, cold fluid outlet 260, solar panel inlet 265,hot fluid inlet 270, and hot fluid outlet 230 can be any hollow conduit,for example a tube or pipe made from either metallic or nonmetallicmaterials, for example copper or polyvinyl chloride. Connections betweenthe various components that guide fluid through the solar heating systemcan be made physically, for example by brazing, or chemically, forexample by applying polyvinyl chloride (PVC) cement.

FIG. 2 shows an exemplary perspective view of a solar collector 100 inone embodiment of the invention. Solar collector 100 can comprise aframe 110 that forms the sides of solar collector 100, and to which thecomponents of solar collector 100 can be attached. In one embodiment,frame 110 can be made of aluminum and consist of two frame sides 111 and113 that are substantially the same size, and a frame top 112 and aframe bottom 113 that are substantially the same size. Frame sides 111and 113 can be aligned in a substantially parallel configuration andtheir ends attached to frame top 112 and frame bottom 113 to form arectangular structure that provides support to the solar collector 100.In one embodiment, frame 110 can be approximately twenty inches wide bysix feet long. However, the shape and size of solar collector 100 asdefined by the frame 110 can be chosen from any number of configurationsto suit a particular design requirement.

An absorption plate 120 can be attached to one of the open sides of theframe 110 so that the side the absorption plate 120 is attached to isenclosed while the opposite side is left open, forming an open box-likestructure. Energy from sunlight 250 incident on the solar collector 100is absorbed by absorption plate 120, which converts the light energyinto heat. Located within the frame 110 and on the surface of absorptionplate 120 that faces the open portion of the solar collector 100 can bea heating coil 150. In one embodiment, heating coil 150 can be a single,hollow conduit that can have a coil inlet 165 on one end, and that canextend longitudinally in a serpentine pattern between the frame bottom114 and the frame top 112 to a coil outlet 175 located on the oppositeend of the heating coil 150 from the coil inlet 165. In otherembodiments, heating coil 150 can extend in a serpentine pattern betweenframe sides 111 and 113, or in other geometries within the solar panel100. Heating coil 150 can be held in place by one or more braces 140that, in one embodiment, can be laid over the heating coil 150 andphysically or chemically attached to the frame and/or the absorptionplate 120 by, for example, rivets, screws, or epoxy, such that theheating coil 150 is securely held in place between the brace 140 and theabsorption plate 120.

In another embodiment, heating coil 150 can comprise two or more lateraltubes 158 aligned in a substantially parallel spaced apart arrangement,for example, with the spacing between the lateral tubes 158 being twoand one-half to three inches. In other embodiments, the size and spacingof the coils can be varied to alter the amount of sunlight 250 incidenton the absorption plate 120, thereby altering the performancecharacteristics of the solar panel 100 to meet specific designrequirements. For example, closer spacing of the lateral tubes 158 willreduce the amount of sunlight incident on the absorption plate 120 andvary the amount of sunlight 250 incident directly on the lateral tubes158, thereby increasing heat absorption on the tops of the lateral tubes158 and decreasing the amount of heat absorption from the absorptionplate 120 on the bottom of the lateral tubes 158.

The coil inlet 165, which can be a rounded pipe or tube, interconnectswith one end of the first lateral tube 158 in the heating coil 150. Theends of each of the lateral tubes 158 are connected by a rounded end cap155 so that fluid flowing in one direction through a lateral tube 158can be routed in a different direction and into an adjacent lateral tube158. The free end of the last lateral tube in the coil is interconnectedwith the coil outlet 175, which can be a rounded hollow conduit, such asa pipe or tube. The coil inlet 165 passes through a collector inlet 160,which can be a hole extending through one of the sides of the frame 110,while the coil outlet passes through a collector outlet 170, which canalso be a hole extending through one of the sides of the frame 110.Accordingly, fluid can enter the heating coil 150 through the coil inlet165, travel in a first direction along the first lateral tube 158, exitthe opposite end of the first lateral tube 158, and flow through the endcap 155 which routes the fluid in a different direction into theadjacent lateral tube 158. The fluid then flows back and forth along thesubsequent lateral tubes 158 and end caps 155 until it reaches the coiloutlet 175 and exits the heating coil 150. In one embodiment, a hotfluid inlet returns the heated fluid to the storage tank 200, where theheated fluid is stored until needed, at which time the hot water canexit the storage tank 200 through a hot fluid outlet.

In other embodiments, rather than directly heating the fluid withinstorage tank 200, solar heating system 10 can further comprise a heatexchanger located between the solar collector 100 and the storage tank200 through which heated fluid from the solar collector 100 travels inorder to transfer heat to the fluid contained in storage tank 200. Forexample, FIG. 3 shows one embodiment in which fluid is circulated bypump 210 within an enclosed system formed by the pump 210, the solarpanel inlet 265, the solar panel 100, a solar panel outlet 275, a heatexchanger 290, and a heat exchanger outlet 295. The circulating fluidtransfers heated fluid from the solar panel 100 into the heat exchanger290 where the heat is transferred to another medium. For example, in oneembodiment, another fluid can be brought into the heat exchanger 290through cold fluid outlet 260 from storage tank 200. The heated fluidcan circulate out of the heat exchanger 290 and can then returned tostorage tank 200 through the hot fluid inlet 270.

FIG. 4 shows an exemplary cross section of a portion of the heating coil150 in one embodiment of the invention. As shown in FIG. 3, a portion oflateral tube 158 has a top 152 and a bottom 154, with both the top 152and bottom 154 being substantially flat. Connecting top 152 and bottom154 are edges 156, which are rounded to give a portion of the lateraltube 158 an elliptical profile. A majority portion of the lateral tubes158 can have an elliptical cross section, while a portion of each of theends of the lateral tubes that interconnect with the coil inlet 165,coil outlet 175, and end caps 155 can have a rounded cross section. Inone embodiment, lateral tube 158 can be formed from a continuous pieceof round tubing or pipe that have been compressed to form the flattenedtop 152 and bottom 154 portions and rounded sides 156. The coil inlet165, lateral tubes 158, end caps 155 and coil outlet 175 can be made outof a variety of metallic or non-metallic materials, for example coppertubing or PVC pipe, and can be of varying size. For example, thecomponents can be made out of half inch or three quarter inch coppertubing.

End caps 155 can be hollow rounded conduits, for example tubes or pipeshaving a rounded cross section that, in one embodiment, aresemi-circular in shape such that fluid entering one end of the end cap155 is directed in a different direction upon exiting the end cap 155.The diameter of each end cap 155 can be such that it either fits snuglywithin or around the ends of each of the lateral tubes 158 to facilitateeasy interconnection of the two parts by physical or chemical means, forexample brazing or PVC cementing. In one embodiment, end caps 255 can bea single piece of conduit. In other embodiments, end caps 155 can becomprised of more than one piece of hollow conduit joined by physical orchemical means to redirect the fluid flow, for example, combinations ofelbow joints and straight sections that render a shape to the end cap155 that may not be semi-circular. Similarly, coil inlet 165 and coiloutlet 175 can be rounded hollow tubes of such a diameter that they canbe fit snugly within or around the ends of lateral tubes 158 tofacilitate easy interconnection of the two parts by physical or chemicalmeans, for example brazing or cementing. The rounded ends of lateraltubes 158 and rounded cross sections of end caps 155 facilitate easy andreliable interconnection of the components without the need forspecialized components requiring expensive custom designs andmanufacturing.

In some embodiments, heating coil 150 can be a single, continuous pieceof conduit with selectively flattened regions in the locationscorresponding to where the lateral tubes 158 would be. In otherembodiments, heating coil 150 can be a single, continuous piece offlattened conduit in which the entire coil exhibits an elliptical crosssection.

The flattened bottom 154 of the lateral tube 158 provides maximumsurface area for heat transfer between the absorption plate 120 and theheating coil 150. Likewise, the flattened top 152 of the lateral tube158 provides maximum surface area for exposure to sunlight 250, therebyproviding maximum heating of the top surface of the heating coil 150.The elliptical cross section of lateral tube 158 also increases thesurface area of fluid that is exposed to a heated interior wall surfacewithin the heating coil 150. Accordingly, the flattened serpentineheating coil 150 not only maximizes the surface area of the heating coil150 that is heated by the solar collector, but also maximizes thesurface area of the fluid within the coil that is exposed to the heatedcoil, thereby improving the overall heat transfer efficiency of thesolar collector. Furthermore, the serpentine path in which the fluidwithin the heating coil travels within the solar collector 100 keeps thefluid within the solar collector 100 for a longer period of time,increasing heat absorption by the fluid. The novel structure of theheating coil 150 therefore exposes a high volume of water to a highamount of heated surface area for a long period of time, therebyimproving the heating efficiency of the solar collector 100.

For example, a conventional flat panel solar collector of average size,for example twenty inches wide by six feet long, typically providesabout 750 BTU of heating output per square foot of panel coverage,resulting in an average rise in fluid temperature of about 2° F. perpass through the solar collector. Similarly sized flat panel solarcollectors embodying the present design can produce up to 1,600 BTU persquare foot of panel coverage, resulting in an average rise in fluidtemperature of about 8° F. per pass through the solar collector 100.This increased performance and heating efficiency can reduce the amountof coverage needed to produce the same degree of fluid heating. Forexample, in a residential hot water heating application, a typicalconventional system requires approximately four twenty inch by six footsolar collectors to provide sufficient hot water for one to two adults.Embodiments of the present design can produce the same hot water outputusing only two solar collectors of the same size, thereby reducinginitial installation costs, reducing long term maintenance costs, andreducing the aesthetic impact of the solar collectors being installed onthe owner's property, typically the roof.

Different embodiments of the invention can incorporate additionalfeatures to improve the performance of the invention, including coatingthe absorption plate 120 and heating coil with materials to increasesunlight absorption, such as black paint, insulating the solar collector100 with thermally protective materials, and enclosing the side of thesolar collector 100 through which sunlight enters with a transparentcovering, such as glass, to reduce thermal loss from wind and otherenvironmental factors. In other embodiments, the solar collector 100 canbe configured in an inverted manner such that the bottom of theabsorption plate 120 faces the incident sunlight 250.

The above detailed description is provided to illustrate exemplaryembodiments and is not intended to be limiting. Although the solarheating system 10 has been shown and described with respect to variousembodiments, it will be apparent to those skilled in the art thatnumerous modifications and variations within the scope of the presentinvention are possible. For example, numerous other materials can beused within the scope of the exemplary structures described as will berecognized by those skilled in the art. Additionally, although variousgeometries have been used to describe various embodiments of theinvention, it will be recognized by those of skill in the art that otherarrangements and geometries of the components can be equally effective.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

1. An apparatus for heating a fluid using solar energy comprising: anabsorption plate exposed to said solar energy; and a heating coilcomprising: a first lateral tube comprising a cylindrical first endportion, a cylindrical second end portion, a flattened top portion, anda flattened bottom portion, said flattened bottom portion being incontact with said absorption plate; a second lateral tube comprising acylindrical first end portion, a cylindrical second end portion, aflattened top portion, and a flattened bottom portion, said flattenedbottom portion being in contact with said absorption plate; and acylindrical end cap connecting said second end portion of said firstlateral tube to said second end portion of said second lateral tube suchthat fluid flowing through said first lateral tube in a first directionis redirected by said end cap into said second lateral tube in a seconddirection.
 2. The apparatus of claim 1, wherein said heating coilcomprises a single, seamless piece of hollow conduit.
 3. The apparatusof claim 1, wherein said heating coil comprises multiple pieces ofhollow conduit that are joined together.
 4. The apparatus of claim 1,further comprising a cylindrical coil inlet, wherein said coil inlet isattached to said first end portion of said first lateral tube.
 5. Theapparatus of claim 1, further comprising a cylindrical coil outlet,wherein said coil outlet is attached to said first end portion of saidsecond lateral tube.
 6. The apparatus of claim 1, wherein saidabsorption plate is made of aluminum.
 7. The apparatus of claim 1,wherein said heating coil is made of copper.
 8. The apparatus of claim1, wherein said heating coil is made of polyvinyl chloride.
 9. A systemfor heating a fluid using solar energy comprising: a pump; a solarcollector comprising: an absorption plate exposed to said solar energy;and a heating coil, said heating coil comprising: a first lateral tubecomprising a cylindrical first end portion, a cylindrical second endportion, a flattened top portion, and a flattened bottom portion, saidflattened bottom portion being in contact with said absorption plate; asecond lateral tube comprising a cylindrical first end portion, acylindrical second end portion, a flattened top portion, and a flattenedbottom portion, said flattened bottom portion being in contact with saidabsorption plate; a cylindrical end cap connecting said second endportion of said first lateral tube to said second end portion of saidsecond lateral tube such that fluid flowing through said first lateraltube in a first direction is redirected by said end cap into said secondlateral tube in a second direction; and a system control that activatessaid pump to force fluid through said solar collector.
 10. The apparatusof claim 9, wherein said heating coil comprises a single, seamless pieceof hollow conduit.
 11. The apparatus of claim 9, wherein said heatingcoil comprises multiple pieces of hollow conduit that are joinedtogether.
 12. The apparatus of claim 9, further comprising a cylindricalcoil inlet, wherein said coil inlet is attached to said first endportion of said first lateral tube.
 13. The apparatus of claim 9,further comprising a cylindrical coil outlet, wherein said coil outletis attached to said first end portion of said second lateral tube. 14.The apparatus of claim 9, wherein said absorption plate is made ofaluminum.
 15. The apparatus of claim 9, wherein said heating coil ismade of copper.
 16. The apparatus of claim 9, wherein said heating coilis made of polyvinyl chloride.
 17. The system of claim 9, furthercomprising a heat exchanger that transfers heat from said fluid exitingsaid solar collector to another medium.
 18. An apparatus for heating afluid using solar energy comprising: an absorption plate exposed to saidsolar energy; and a heating coil comprising: a first lateral tubecomprising a first end portion, a second end portion, a flattened topportion, and a flattened bottom portion, said flattened bottom portionbeing in contact with said absorption plate; a second lateral tubecomprising a first end portion, a second end portion, a flattened topportion, and a flattened bottom portion, said flattened bottom portionbeing in contact with said absorption plate; and an end cap connectingsaid second end portion of said first lateral tube to said second endportion of said second lateral tube such that fluid flowing through saidfirst lateral tube in a first direction is redirected by said end capinto said second lateral tube in a second direction.
 19. The apparatusof claim 18, wherein said heating coil comprises a single, seamlesspiece of hollow conduit.
 20. The apparatus of claim 18, wherein saidheating coil comprises multiple pieces of hollow conduit that are joinedtogether.